Many valve types have been employed for stopping and controlling the flow of fluids in a pipe or other flow path. Each type of valve offers certain advantages and disadvantages. Some valve types include plug valves, ball valves, stop or globe valves, angle valves, butterfly valves, and gate valves.
Wedge gate valves have a gate shaped as a wedge, with two opposed inclined planar faces (typically metal) that each seal against part of a valve seat of the body of the valve. Both of the faces of the gate and the corresponding surfaces of the valve seat are typically machined to allow the gate to form a seal. Manufacturing tolerances and deposition of material during use of the valve may cause problems forming seals, either at installation or later in the life of gate valve. O-rings may be recessed in each of the metal faces to limit leakage of such a valve, but this typically requires machining during manufacture, and thus, additional costs. Wedge gate valves typically have a recess at the base of the valve body to receive the tip of the wedge shaped gate. This recess can fill with debris, impeding full gate closure.
Parallel slide gate valves typically include a gate having two members separated by a spring or other biasing member. The gate slides into a sealing position between parallel valve seats. For example, as shown in FIG. 1, a gate valve 10 may include a valve body 12 having an internal surface 14, upstream opening 16, a downstream opening 18, and a generally horizontal internal passage 20 therebetween for accepting a flow of fluid indicated by arrow A. The internal surface 14 defines a vertically oriented internal chamber 22 that intersects the internal passage 20 approximately midway between the upstream opening 16 and the downstream opening 18. The internal chamber 22 provides room for a gate 24 to move vertically out of and into the internal passage 20 to open and close the gate valve 10. The gate 24 includes two generally planar halves 24a, 24b, connected by a carrier ring 26 and bracket 28. A spring 30 urges the halves 24a, 24b apart, pushing one or both halves 24a, 24b against valve seats 32a, 32b when the gate valve 10 is closed, blocking the internal passage 20. When the gate valve 10 is open, the spring 30 urges the halves 24a, 24b apart against the bracket 28, which limits the distance that the halves 24a, 24b may travel from one another, such that the halves 24a, 24b do not separate within the internal chamber 22. The gate valve 10 also includes a valve stem 34 configured to vertically move the gate 24 and a handle 36 or other means (e.g., a motor) to move the valve stem 34. The valve stem 34 may be threaded or unthreaded, and may or may not rotate to move the gate 24.
Failure of the bracket 28 may cause the halves 24a, 24b to become decoupled from one another, such that the gate 24 cannot be moved back into the internal passage 20 to close the gate valve 10. Furthermore, failure of the bracket 28 may cause the halves 24a, 24b, the carrier ring 26, the bracket 28, and/or the spring 30 to be flushed downstream with the fluid. It would be beneficial to provide a valve design that alleviates some or all of these drawbacks.